The invention relates to a method of generating a laser marking in a security document by means of at least one laser beam, the security document having at least one laser-markable layer and also at least one reflecting layer which overlaps at least partly with the at least one laser-markable layer and has opaque regions.
The introduction of laser marks in security documents of this kind as protection against copying is known from DE 44 10 431 A1. An identity card or similar data carrier is in this case formed with a laser-markable layer, a reflecting metal layer and a transparent card covering layer, in this sequence. With the aid of a laser beam, congruent identifications are introduced through the card covering layer into the reflecting metal layer and the laser-markable layer. The laser-markable layer may in this case be applied as a coating on a card core layer, the reflecting metal layer not covering the laser-markable layer completely and it consequently being possible for identifications to be introduced not only into the reflecting metal layer but also into the laser-markable layer.
Furthermore, a method of producing a data carrier which has a laser-markable layer and a transparent, optically variable layer overlapping at least in certain regions therewith is known from WO 01/62509 A1. Optically variable layers give different impressions, such as for example show different colors, from different viewing angles. The transparent, optically variable layer is arranged on the side of the laser-markable layer that is facing the viewer and is largely transparent to the laser radiation that is used. With a laser beam, visually perceptible markings, in particular black markings, are recorded in the laser-markable layer through the optically variable layer, the optically variable effect being clearly visible in particular in the regions of the optically variable layer that lie over the laser marking generated. By contrast, the optically variable effect is less clearly visible in the other regions of the laser-markable layer that are covered by the optically variable layer.
Security elements with opaque, reflecting regions according to DE 44 10 431 A1, on the other hand, are visually clearly recognizable independently of the background, on account of the high reflectivity of the opaque metal regions. The reflecting metal layer is cut through congruently during the laser marking of a laser-markable layer arranged thereunder, so that in the openings produced in the reflecting metal layer only material that has been altered by the laser irradiation is visible. It is not possible to produce an informational content of the laser marking in the laser-markable layer that is independent of the formation of the openings in the reflecting metal layer.